This invention relates to turnbutton latches and is particularly concerned with the provision of a better turnbutton latch than has been available heretofore.
Turnbutton latches provide an easily operated latch of the push-to-close turn-to-open type that requires little manual dexterity, that resists opening during rough handling, and that is especially suitable for students' book bags and travel bags, for example. One type of prior turnbutton latch is disclosed in U.S. Pat. No. 2,487,895 to Rounds. In that latch a post of clover-leaf design integral with a base is concentric with a stud on which a locking member of similar design is mounted by means of a nut screwed onto the end of the stud. A coil spring supported concentrically in the stud has one end engaging the locking member to bias the locking member to a closed position and has the other end bent to form a trigger and also to form a catch which holds the locking member in its open position until the trigger is depressed by the female member of the latch. A pin projecting from the base into a slot of the locking member limits the turning movement of the locking member. In the device of Rounds a single spring must be critically shaped and relied upon to perform a plurality of functions. The device does not have a smooth exterior and is not constructed of parts that are easily mass-produced, easily assembled, and designed to perform their intended functions reliably over long periods of time.
Another type of turnbutton latch, presently marketed as part of a case for binoculars, provides a better exterior appearance, but the device is constructed almost entirely of sheet metal and has certain disadvantages. The turnbutton is a multi-part sheet metal shell supported on an end wall of a hollow sheet metal stud by means of a rivet which serves as a pivot for the turnbutton. A sheet metal tab of the turnbutton projects into an arcuate slot in the end wall of the stud and engages one arm of a wire spring which biases the turnbutton to its closed position. A sheet metal base closes the opposite end of the stud and supports a trigger, one part of which is fairly rigid sheet metal and another part of which is a leaf spring having a tab which enters a slot in the base to support the trigger on the base. A sheet metal lug of the trigger passes through a hole in the end wall of the stud and enters a hole in the turnbutton to retain the turnbutton in its open position until the trigger is depressed. When the turnbutton is turned from its closed position toward its open position, the lug is disengaged from the hole in the turnbutton by a camming action but then snaps into another hole of the turnbutton when the turnbutton reaches its open position. The construction of this type of turnbutton latch is rather flimsy and does not appear to be likely to provide reliable operation with rough handling over long periods of time. There is a gap between the opposing surfaces of the turnbutton and the stud, at which the tab can be seen extending from the turnbutton into the stud and the lug can be seen extending from the stud into the turnbutton, and the central rivet support for the turnbutton is inadequate to prevent some wobbling of the turnbutton.